Cooling system and methods for cooling interior volumes of cargo trailers

ABSTRACT

A system for controlling a temperature a within an interior volume of a cargo trailer adapted to transport perishable goods is described herein. The system includes a fluid distribution assembly and a monitoring system. The fluid distribution assembly is configured to selectively channel a flow of cryogenic cooling fluid into the cargo trailer interior volume to facilitate adjusting a temperature within the interior volume. The monitoring system includes at least one sensor for sensing an environmental parameter of the cargo trailer, and a controller coupled to the sensor and to the fluid distribution assembly. The controller is configured to receive a monitoring signal indicative of the sensed environmental parameter, determine an environmental condition of the cargo trailer as a function of the environmental parameter, and provide a notification signal if the determined environmental condition is different than a predefined environmental condition.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a continuation of U.S. patent application Ser. No.13/926,728, filed Jun. 25, 2013, which claims the benefit of U.S.Provisional Application No. 61/664,075, filed Jun. 25, 2012, thedisclosures of which are incorporated herein by reference.

TECHNICAL FIELD

The subject matter disclosed herein relates generally to refrigeratedcargo trailers and more particularly, to a cooling system and methodsfor cooling interior volumes of cargo trailers.

BACKGROUND OF THE INVENTION

To facilitate the transportation of perishable goods, cargo vessels suchas, for example, truck trailers and/or containers include a trailerrefrigeration unit (TRU) to maintain the temperature of the cargocompartment at the desired temperature. Products at risk of damage fromelevated ambient temperature may be maintained at “room temperature”(approximately 20° C./68° F.), while refrigerated goods are typicallyheld slightly above the freezing point (1° C./35° F.), and frozenproducts may be stored at a variety of temperature set points between−15° C./0° F. and −30° C./−20° F. The cargo may contain a variety ofconsumer products such as produce, frozen and refrigerated meat, dairy,candy, pharmaceuticals, and flowers.

Contemporary TRUs with diesel-powered compressor systems provide therequired cooling performance, but are becoming less attractive from aneconomic standpoint due to the cost of maintenance, fueling, andregulatory compliance. Additionally, society places substantial pressureon the users of TRUs to reduce environmental impact, particularly inurban areas where noise and exhaust emissions are perceived to beespecially problematic.

To provide an alternative method of cargo cooling with fewerenvironmental drawbacks than diesel TRUs, a cryogenic cooling system(CCS) utilizes the stored thermal energy of liquid nitrogen (LN₂) forthe purpose of maintaining cargo temperature. Two general types of CCSmay be employed—“direct” systems where the LN₂ is dispersed directlyinto the cargo compartment, and “indirect” systems that use anevaporator (similar to that of compressor-based system) and circulatingfans to transfer heat from the cargo into the cooling medium.

The direct method of injecting LN₂ is preferred due to its superiorefficiency as compared to indirect systems—nearly all of the potentialheat energy absorption of the cooling medium is realized through directinteraction between the LN₂ and the cargo, and no defrost cycles arerequired to remove ice from an evaporator (icing can occur whenever theevaporator surface temperature is lower than the freezing point of waterand moisture is present in the air). Since fuel is necessarily limitedby the size of the LN₂ vessel and thus efficiency is an importantparameter in maximizing the utility of this system, direct systems canhave a significant advantage in energy efficiency. Additionally, asdirect LN₂ systems do not require the use of circulation fans during thecooling cycle, they have lower electrical power consumption during thecooling cycle (important as the trailer is often not connected to atractor or shore power during the lengthy loading and staging process),substantially lessened noise emissions, and) and decreased drying offood.

Some refrigerated vehicles may include direct LN₂ systems thatdistribute LN₂ through a spray tube arrangement, and simultaneouslythrough an evaporator arrangement. The LN₂ flows through the evaporatorarrangement and is converted to gaseous nitrogen which is used to drivea fan for drawing air into the space to achieve environmental control.However, the introduction of liquid nitrogen directly into the enclosedtrailer space presents a safety risk to operators because of thepossibility of entering an atmosphere that contains dangerous levels ofgaseous nitrogen. For example, as the liquid nitrogen is sprayed withinthe space, air is drawn into the space, however, serious safety risksare present due to the significant amount of gaseous nitrogen occupyingthe space.

Accordingly, new features are necessary to improve the safety andmonitoring of refrigerated vehicles that include cryogenic coolingsystems to reduce the potential health risks exposed to a vehicleoperator when operating the refrigerated vehicles and loading andunloading products from the refrigerated trailers. The present inventionis directed to satisfying these needs.

SUMMARY OF THE INVENTION

In one aspect of the present invention, a system for controlling atemperature a within an interior volume of a cargo trailer adapted totransport perishable goods is provided. The system includes a fluiddistribution assembly and a monitoring system operatively coupled to thefluid distribution assembly for selectively channeling a flow ofcryogenic cooling fluid into the cargo trailer interior volume tofacilitate adjusting a temperature within the interior volume. Themonitoring system includes at least one sensor for sensing anenvironmental parameter of the cargo trailer, and a controller coupledto the sensor and to the fluid distribution assembly. The controller isconfigured to receive a monitoring signal indicative of the sensedenvironmental parameter, determine an environmental condition of thecargo trailer as a function of the environmental parameter, and providea notification signal if the determined environmental condition isdifferent than a predefined environmental condition.

In another aspect of the present invention, a monitoring system for usein controlling a temperature a within an interior volume of a cargotrailer adapted to transport perishable goods is provided. The cargotrailer includes a fluid distribution assembly for channeling a flow ofcryogenic cooling fluid into the cargo trailer interior volume tofacilitate adjusting a temperature within the interior volume. Themonitoring system includes at least one sensor for sensing anenvironmental parameter of the cargo trailer and a controller coupled tothe sensor and to the fluid distribution assembly. The controller isconfigured to receive, from the at least one sensor, a monitoring signalindicative of the sensed environmental parameter, determine anenvironmental condition of the cargo trailer as a function of theenvironmental parameter, and provide a notification signal if thedetermined environmental condition is different than a predefinedenvironmental condition.

In yet another aspect of the present invention, a method of controllinga temperature a within an interior volume of a cargo trailer isprovided. The cargo trailer includes a fluid distribution assembly forchanneling a flow of cryogenic cooling fluid into the cargo trailerinterior volume. The method includes receiving, from a sensor, amonitoring signal indicative of a sensed environmental parameter,determining an environmental condition of the cargo trailer as afunction of the environmental parameter, and providing a notificationsignal to an operator if the determined environmental condition isdifferent than a predefined environmental condition.

BRIEF DESCRIPTION OF THE DRAWINGS

Other advantages of the present invention will be readily appreciated asthe same becomes better understood by reference to the followingdetailed description when considered in connection with the accompanyingdrawings wherein:

FIG. 1 is a perspective view of an exemplary system that may be used forcontrolling a temperature within an interior volume of a cargo trailer,according to an embodiment of the present invention;

FIG. 2 is a perspective view of a portion of the system shown in FIG. 1and taken along area 2;

FIG. 3 is a perspective view of a portion of the system shown in FIG. 1and taken along area 3;

FIG. 4 is a perspective view of an interior volume of a cargo trailerincluding a portion of the system shown in FIG. 1, according to anembodiment of the present invention;

FIG. 5 is another perspective view of the cargo trailer shown in FIG. 4;

FIG. 6 is a schematic representation of the system shown in FIG. 1,according to an embodiment of the present invention;

FIG. 7 is schematic view of a monitoring system that may be used withthe system shown in FIG. 1, according to an embodiment of the presentinvention; and

FIG. 8 is a flowchart of a method that may be used with the system shownin FIG. 1 for controlling a temperature within an interior volume of acargo trailer, according to an embodiment of the invention.

Corresponding reference characters indicate corresponding partsthroughout the drawings.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT

With reference to the drawings and in operation, the present inventionovercomes at least some of the disadvantages of known trailerrefrigeration systems by providing a system that includes a monitoringsystem that determines an environmental condition of a cargo trailer andprovides a notification to the operator if the environmental conditionis hazardous to the operator. In addition, the monitoring system mayrestrict access to the cargo trailer based on the determinedenvironmental condition. More specifically, the monitoring system willdetermine the environmental condition as a function of sensedenvironmental parameters such as, for example, temperature, pressure,oxygen levels, and/or nitrogen levels, and notify the operator if thedetermined environmental condition is different than a predefinedenvironmental condition. In addition, the system includes fluiddistribution assembly for channeling cryogenic cooling fluid into aninterior volume of the cargo trailer to control a interior temperature.The monitoring system monitors the operation of the fluid distributionassembly and adjusts a flow of the cryogenic cooling fluid based on thesensed environmental parameters. By providing a system that monitors andcontrols an operation of a cryogenic cooling fluid distributionassembly, the health risks exposed to an operator is significantlyreduce as compared to known refrigeration system. Thus the cost ofoperating the trailer refrigeration system is reduced.

In general, the system 10 includes a cargo trailer for transportingproducts and/or cargo that are required to be maintained within aspecific temperature range during transport of the cargo. For example,the system 10 may be adapted to transport cargo including refrigeratedproducts such as, for example, medical supplies, food, perishable goods,farm products, flowers, commercial goods, and/or any suitable items thatrequire a temperature controlled environment during transport. In theillustrated embodiment, the system 10 includes a cooling fluiddistribution assembly for channeling cooling fluid into the cargotrailer to maintain a refrigerated space with the cargo trailer. Thesystem 10 also includes a monitoring system that is adapted to monitorthe condition of the cargo trailer and/or the cooling fluid distributionassembly and to notify an operator of the condition of the system 10.For example, in one embodiment, the monitoring system may notify theoperator of an operating condition of the fluid distribution assembly.The monitoring system may also notify the operator of potential healthrisks present within the refrigerated space such as, for example,elevated levels of cooling fluid and/or reduced levels of breathable airwithin the refrigerated space. Moreover, the monitoring system may alsoadjust an operation of the fluid distribution assembly based on themonitored conditions of the refrigerated space and/or the fluiddistribution assembly. In another embodiment, the system 10 may alsoinclude a heated space, wherein the monitoring system is adapted tomonitor a condition of the heated space and notify the operator of themonitored condition.

A selected embodiment of the invention will now be explained withreference to the drawings. It will be apparent to those skilled in theart from this disclosure that the following description of theembodiment of the invention is provided for illustration only and notfor the purpose of limiting the invention as defined by the appendedclaims and their equivalents.

FIG. 1 is a perspective view of a system 10 that may be used forcontrolling a temperature within an interior volume 12 of a cargotrailer 14. FIGS. 2-5 are perspective views of the system 10. FIG. 6 isa schematic representation of the system 10. In the illustratedembodiment, the system 10 includes a fluid distribution assembly 16 forchanneling a flow of cooling fluid into the interior volume 12, aventilation assembly 18 for discharging the cryogenic fluid from theinterior volume 12, a cargo access assembly 20 to selectively provideaccess into the interior volume 12, and a monitoring system 22operatively coupled to the fluid distribution assembly 16, theventilation assembly 18, and the cargo access assembly 20.

In the illustrated embodiment, the cargo trailer 14 includes a body 24that includes a front wall 26, a rear wall 28, a top wall 30, a bottomwall 32, and a pair of sidewalls 34 that extend between the front wall26 and the rear wall 28, and between the top wall 30 and the bottom wall32. Each wall 26-34 includes an inner surface 36 that defines theinterior volume 12 therein. In addition, each wall 26-34 includesthermally insulated material (not shown) having an insulation value tofacilitate preventing a transfer of heat between the interior volume 12and ambient air 38 to thermally insulate the interior volume 12. Thecargo trailer 14 also includes at least one access door 40 toselectively provide access to the interior volume 12 to enable loadingan unloading of cargo 42 into the cargo trailer 14. In one embodiment,the interior volume 12 may include a plurality of thermally regulatedzones 44 extending between the front wall 26 and the rear wall 28, andmay include a different ambient temperature within each zone 44. Inaddition, the cargo trailer 14 may include a plurality of dividers 46positioned between each of the plurality of zones 44 to define aplurality of compartments 48 within the interior volume 12. In oneembodiment, each divider 46 may be removable coupled to the innersurface 36 to enable an operator to selectively couple each divider 46within the cargo trailer 14 to adjust a volume defined by eachcompartment 48 and/or a number of compartments 48 defined within theinterior volume 12. In one embodiment, the dividers 46 may includethermal insulation material to facilitate thermally isolating adjacentcompartments 48 and/or zones 44. In another embodiment, the dividers 46may be configured to provide a thermal differential and/or an airpressure differential between adjacent zones 44. In addition, thedividers 46 may include, but are not limited to including, a wall, apartition, a curtain, a fence, and air curtain, and/or any suitabledivider that enables each zone and/or compartment to include anindependently regulated ambient temperature.

In the illustrated embodiment, the cargo trailer 14 is configured to becoupled to a vehicle such as, for example, a truck (not shown) fortransporting the cargo trailer 14. In another embodiment, the cargotrailer 14 may in integrally formed with the vehicle. In addition, thecargo trailer 14 may be configured to be transported by ship, railcar,airplane, and/or any suitable vehicle for transporting the cargo trailer14.

In the illustrated embodiment, the fluid distribution assembly 16 iscoupled to the cargo trailer 14 and adapted to channel a flow of coolingfluid, represented by arrow 50, into the interior volume 12 of the cargotrailer 14 to selectively adjust an ambient temperature within theinterior volume 12 to facilitate maintaining a temperature of the cargo42. In the illustrated embodiment, the fluid distribution assembly 16 isconfigured to channel a flow of cryogenic fluid 50 such as for exampleliquid nitrogen. The cryogenic fluid 50 may be in a liquid phase, agaseous phase, and/or a liquid-gaseous phase. In one embodiment, thefluid distribution assembly 16 may channel any suitable cooling fluidsuch, for example or liquid carbon dioxide (CO₂) and/or any othersuitable liquid cryogen. In the illustrated embodiment, the fluiddistribution assembly 16 includes a cryogenic fluid supply tank 52 thatis coupled to the cargo trailer 14 for storing a volume of cryogenicfluid 50, a plurality of spray nozzle assemblies 54 positioned withinthe interior volume 12 for discharging a flow of cryogenic fluid 50 intothe interior volume 12, and at least one fluid conduit 56 that iscoupled between the cryogenic fluid supply tank 52 and the spray nozzleassemblies 54 for channeling the cryogenic fluid 50 from the cryogenicfluid supply tank 52 to each of the spray nozzle assemblies 54. Aplurality of control valves 58 are coupled to the fluid conduit 56and/or the spray nozzle assemblies 54 for selectively channeling a flowof cryogenic fluid 50 to the interior volume 12 through the spray nozzleassemblies 54. In one embodiment, the control valves 58 may bepositioned adjacent to each spray nozzle assembly 54. In anotherembodiment, the control valves 58 may be positioned adjacent to thefluid supply tank 52 and/or positioned at any location within the cargotrailer 14 that enables the system 10 to function as described herein.

In the illustrated embodiment, the spray nozzle assemblies 54 aremounted to the inner surface 36 of the top wall 30 and are positionedwithin the interior volume 12. Each spray nozzle assembly 54 isconfigured to facilitate a cryogenic fluid phase change within thecryogenic fluid 50 from a liquid cryogenic fluid to a gaseous cryogenicfluid and to discharge the gaseous cryogenic fluid 50 into the interiorvolume 12 and to facilitate adjusting an ambient temperature within theinterior volume 12. In one embodiment, the system 10 may include a spraynozzle assembly 54 positioned within each zone 44 to independentlyadjust an ambient temperature within each zone 44 by selectivelychanneling a flow of cryogenic fluid 50 to each zone 44 independently.Each spray nozzle assembly 54 includes a spray bar 60, a plurality ofnozzles 62 coupled to the spray bar 60 for discharging the cryogenicfluid 50 from the spray bar 60, and a fan 64 positioned adjacent to thespray bar 60 to facilitate a mixing of the cryogenic fluid 50 beingdischarged from the nozzles 62 within the interior volume 12. Thenozzles 62 are preferably arranged in a fan-like array to spray thecryogenic fluid 50 in all horizontal directions. The spray nozzleassemblies 54 are positioned throughout the interior volume 12 tofacilitate cooling the interior volume 12.

In the illustrated embodiment, the cryogenic fluid supply tank 52 ismounted to an outer surface of the cargo trailer 14 to facilitate accessto the fluid supply tank 52 to enable an operator to fill and re-fillthe fluid supply tank 52 with cryogenic fluid 50. In one embodiment, thefluid supply tank 52 may also include a discharge control valve (notshown) that is coupled to the fluid supply tank 52 to enable the coolingfluid to be discharged from the fluid supply tank 52 during tankmaintenance and/or to facilitate reducing an internal tank pressure. Inanother embodiment, the fluid supply tank 52 may be positioned withinthe cargo trailer walls 26-34.

In the illustrated embodiment, the ventilation assembly 18 is configuredto discharge a cryogenic gas 50 from the interior volume 12, andincludes a fan assembly 66 and at least one opening 68 extending throughthe cargo trailer 14 to couple the interior volume 12 in fluidcommunication with the ambient air 38 through the opening 68. A hatchassembly 70 extends over the opening 68 and is configured to selectivelychannel air and/or cryogenic fluid 50 through the opening 68. The fanassembly 66 is configured to channel a flow of air into the interiorvolume 12 and through the opening 68 to purge the cryogenic fluid 50from the interior volume 12 to the exterior of the cargo trailer 14. Inone embodiment, the fan assembly 66 is coupled to an exterior of thecargo trailer 14. Alternatively, the fan assembly 66 may be located atany position within the cargo trailer 14 to enable the ventilationsystem 18 to function as described herein. In one embodiment, a louversystem (not shown) may be coupled to the fan assembly 66 to selectivelychannel ambient air 38 though the fan assembly 66 and into the interiorvolume 12. In the illustrated embodiment, the ventilation assembly 18 isconfigured to channel a flow of ambient air 38 from the cargo trailerexterior through the interior volume 12 to move the cooling fluid 50through the opening 68 during a purge operation to purge gaseouscryogenic fluid 50 from the interior volume 12 by in-flow of ambient airto create a breathable atmosphere within in the interior volume 12. Inanother embodiment, the ventilation system 18 is configured to dischargethe cryogenic fluid 50 from the interior volume 12 through the cargoaccess door 40. In one embodiment, the ventilation assembly 18 may alsoinclude an air supply tank (not shown) and/or an oxygen tank (not shown)that is coupled in fluid communication with the fan assembly 66 forchanneling a flow of air and/or oxygen into the interior volume 12 toincrease oxygen levels within the interior volume 12. In addition, theventilation assembly 18 may also include a evaporator assembly 72 thatis coupled to the fluid distribution assembly 16 for channeling a flowof ambient air 38 across a plurality conduits (not shown) that containcryogenic fluid to facilitate cooling the ambient air 38 being channeledinto the interior volume 12. In another embodiment, the ventilationassembly 18 may also include a vacuum system (not shown) for removingthe cryogenic fluid 50 from the interior volume 12.

The cargo access assembly 20 is coupled to the cargo trailer 14 tofacilitate access into the interior volume 12. In the illustratedembodiment, the cargo access assembly 20 includes a latch assembly 74mounted to the cargo sidewall 34 and a safety locking member 76 that isremovably coupled to the latch assembly 74 to facilitate preventing anoperator from entering the interior volume 12. The latch assembly 74includes an electro-mechanical latch that is operable between a lockedposition and an unlocked position. In the locked position, the safetylocking member 76 is coupled to the latch assembly 74 to prevent anoperator from removing the safety locking member 76 from the latchassembly 74. In the unlocked position, the safety locking member 76 isdecoupled from the latch assembly 74 to enable the operator to removethe safety locking member 76 from the latch assembly 74 to access theinterior volume 12. In the illustrated embodiment, the safety lockingmember 76 may include a cable assembly 77 that extends between thesidewalls 34. In one embodiment, the safety locking member 76 mayinclude the cargo access door 40 to selectively lock and unlock theaccess door 40 to provide access to the interior volume 12. In anotherembodiment, the safety locking member 76 may include a gate, a door, anarm, a belt, and/or any suitable device that may prevent access into theinterior volume 12. In addition, the cargo access assembly 20 mayinclude a plurality of barriers (not shown) positioned with the interiorvolume 12 and defining each of the plurality of compartments 48 withinthe interior volume 12. Each barrier may include a door and a latchassembly 74 coupled to the door to selectively provide access into thecorresponding compartment 48.

In the illustrated embodiment, the monitoring system 22 includes aplurality of sensors 78, a controller 80 that is coupled incommunication with each of the plurality of sensors 78, and a displaydevice 82 that is coupled to the controller 80 for displayinginformation to the operator. Each sensor 78 detects various parametersrelative to the operation of the fluid distribution assembly 16, theventilation assembly 18, the cargo access assembly 20, and theenvironmental condition of the cargo trailer 14 and transmits a signalindicative of the sensed parameter to the controller 80. Sensors 78 mayinclude, but are not limited to only including, position sensors,vibration sensors, acceleration sensors, temperature sensors, pressuresensors, flow sensors, motion sensors, and/or any other sensors thatsense various parameters relative to the operation of the system 10 andthe environmental condition of the cargo trailer 14. As used herein, theterm “parameters” refers to physical properties whose values can be usedto define the operational mode, orientation, position, and operatingconditions of the fluid distribution assembly 16, the ventilationassembly 18, the cargo access assembly 20, and/or the cargo trailer 14,such as, but not limited to, an operating mode, an interior volumetemperature, an exterior temperature, an interior volume pressure, abarometric pressure, a supply tank pressure, oxygen levels, nitrogenlevels, a cooling fluid temperature, a fluid supply pressure, a controlvalve operation, vibrations and accelerations at defined locations.

In the illustrated embodiment, the monitoring system 22 includes one ormore temperature sensors 84, gas sensors 86, position sensors 88,proximity sensors 90, pressure sensors 92, and/or flow sensors 94. Thetemperature sensors 84 are configured to sense an ambient temperaturewithin the interior volume 12 and/or a temperature of the cargo 42. Thegas sensors 86 are configured to sense a presence and/or an amount ofgas present within the interior volume 12. The sensed gases may include,but are not limited to including, oxygen, nitrogen, carbon dioxideand/or any suitable gas that enables the monitoring system 22 tofunction as described herein. The position sensor 88 senses a positionof the fluid control valve 58, a position of the cargo access door 40,and/or a position of the latch assembly 74. The proximity sensors 90sense a motion within the interior volume 12. The pressure sensors 92sense a pressure within the interior volume 12, an external airpressure, a fluid pressure within the fluid distribution assembly 16,and/or a fluid pressure within the fluid supply tank 52. The flow sensor94 senses a flow of cooling fluid being channeled through the fluiddistribution assembly 16.

In the illustrated embodiment, the controller 80 includes a processor 96and a memory device 98. The processor 96 executes various programs, andthereby controls other components of the system 10 according to userinstructions and data received from the display device 82. The memorydevice 98 stores programs and information used by the processor 96. Theprocessor 96 includes any suitable programmable circuit which mayinclude one or more systems and microcontrollers, microprocessors,reduced instruction set circuits (RISC), application specific integratedcircuits (ASIC), programmable logic circuits (PLC), field programmablegate arrays (FPGA), and any other circuit capable of executing thefunctions described herein. The above examples are exemplary only, andthus are not intended to limit in any way the definition and/or meaningof the term “processor.” The memory device 98 includes a computerreadable medium, such as, without limitation, random access memory(RAM), read-only memory (ROM), erasable programmable read-only memory(EPROM), flash memory, a hard disk drive, a solid state drive, adiskette, a flash drive, a compact disc, a digital video disc, and/orany suitable device that enables the processor 96 to store, retrieve,and/or execute instructions and/or data.

The memory device 98 may also include a database 100 that containsinformation on a variety of matters, such as, for example, environmentalparameters, predefined environmental conditions, temperatures,pressures, predefined operating conditions, and/or audio and visualimage data for producing visual and/or audible notifications and/oralarms on displayed on the display device 82.

In the exemplary embodiment, the controller 80 includes a controlinterface module 102 that is coupled to the fluid distribution assembly16, the ventilation assembly 18, and the cargo access assembly 20 forcontrolling an operation of the control valves 58, fan 64, fan assembly66, and latch assembly 74. In addition, the controller 80 also includesa sensor interface module 104 that is coupled to each sensor 78 such as,for example, sensors 84-94 for receiving and transmitting data to andfrom each sensor 78. Each sensor 78 may transmit a signal continuously,periodically, or only once and/or any other signal timing that enablesmonitoring system 22 to function as described herein. Moreover, eachsensor 78 may transmit a signal either in an analog form or in a digitalform.

The display device 82 is coupled to the controller 80 for displayinginformation to a user and to receive user selection input indicative ofthe user's selection and transmit the user selection input to thecontroller 80 to enable the user to interact with the system 10. Thedisplay device 82 includes a display 106 and a user input device 108.The display 106 may be positioned within the interior of the cargotrailer 14, the exterior of the cargo trailer 14, within a vehicle (notshown) and/or any suitable location that enables a user to viewinformation being displayed on the display 106. The display 106includes, without limitation, a flat panel display, such as a cathoderay tube display (CRT), a liquid crystal display (LCD), a light-emittingdiode display (LED), active-matrix organic light-emitting diode(AMOLED), a plasma display, and/or any suitable visual output devicecapable of displaying graphical data and/or text to a user. Moreover,the user input device 108 includes, without limitation, a keyboard, akeypad, a touch-sensitive screen, a scroll wheel, a pointing device, abarcode reader, a magnetic card reader, a radio frequency identification(RFID) card reader, an audio input device employing speech-recognitionsoftware, and/or any suitable device that enables a user to input datainto the controller 80 and/or to retrieve data from the controller 80.Alternatively, a single component, such as a touch screen, a capacitivetouch screen, and/or a touchless screen, may function as both thedisplay 106 and as the user input device 108.

Various connections are available between the controller 80, the displaydevice 82, the sensors 78, the control valves 58, the fan 64, the fanassembly 66, and the latch assembly 74. Such connections may include,without limitation, an electrical conductor, a low-level serial dataconnection, such as Recommended Standard (RS) 232 or RS-485, ahigh-level serial data connection, such as Universal Serial Bus (USB) orInstitute of Electrical and Electronics Engineers (IEEE) 1394 (a/k/aFIREWIRE), a parallel data connection, such as IEEE 1284 or IEEE 488, ashort-range wireless communication channel such as BLUETOOTH, and/or aprivate (e.g., inaccessible outside the system 10) network connection,whether wired or wireless.

During operation of the system 10, the liquid supply tank 52 is filledwith liquid nitrogen at, for example, about −196° C. Prior to loadingthe interior volume 12 with cargo such as, for example, food, themonitoring system 22 may pre-cool the interior volume 12 by operatingone or more control valves 58 to channel the cryogenic fluid 50, e.g.liquid nitrogen, to the spray nozzles 62 to spray the liquid nitrogenwithin the interior volume 12. As the liquid nitrogen is discharged intothe interior volume 12, the liquid nitrogen evaporates and pre-cools theinterior volume 12, the cargo trailer inner surface 36 and all internalelements, to a desired temperature. This may be done while the truck isin transit to, or awaits loading at, a loading site. The monitoringsystem 22 positions the control valves 58 completely or partially closedwhen the desired interior temperature is reached. During this operation,an atmosphere of almost pure gaseous nitrogen is created inside theinterior volume 12, which may create a potentially hazardous area to anoperator. Accordingly, the interior volume 12 must be purged with airprior to the loading operation. The monitoring system 22 performs thepurging operation by operating the ventilation assembly 18 to open thehatch assembly 70 and operate the fan assembly 66 to channel air throughthe interior volume 12 and discharge the gaseous nitrogen from the cargotrailer 14. During this operation, the temperature of the interiorvolume 12 may be monitored to enable the monitoring system 22 toselectively channel air through the evaporator assembly 72 to facilitatecontrolling the temperature of air entering the interior volume 12.Alternatively, the ambient air is not cooled and the temperature of theinterior volume 12 is monitored to assure that it stays within a propertemperature range.

Once the refrigeration space has been filled with air and a suitableatmosphere has been created, a food-loading operation is performed.During this operation, the monitoring system 22 operates the cargoaccess assembly 20 to enable an operator to enter the interior volume 12to load the cargo 42. During the loading operation, the environmentalcondition of the interior volume 12 is monitored and monitoring system22 operates the fluid distribution assembly 16 as necessary to maintainthe desired interior temperature.

Once the food has been loaded, the door 40 is closed, and the truck istransported to its first destination. During transport, the monitoringsystem 22 monitors the interior volume 12 and operates the fluiddistribution assembly 16 to adjust the internal temperature within theinterior volume 12. When the cargo trailer 14 reaches a destination, itis necessary to purge gaseous nitrogen from the interior volume 12 andthe purging operation is repeated.

The above operations are repeated, to enable the cargo trailer 14 totravel to numerous unloading sites, while ensuring that the cargo 42 ismaintained at an appropriate temperature.

FIG. 7 is schematic view of the controller 80, according to anembodiment of the present invention. In the illustrated embodiment, thecontroller 80 includes a flow distribution module 110, a cargo accessmodule 112, a venting control module 114, a display module 116, and anenvironmental monitoring module 118. The flow distribution module 110receives data from the sensors 78 indicative of a flow of cryogenicfluid 50 through the fluid distribution assembly 16 and monitors acondition of the fluid distribution assembly 16 as a function of thesensed flow. The flow distribution module 110 also operates the fluiddistribution assembly 16 as a function of data received from theenvironmental monitoring module 118 and input from the user. The cargoaccess module 112 operates the cargo access assembly 20 as a function ofuser input and data received from the environmental monitoring module118. The venting control module 114 operates the ventilation assembly 18as a function of user input and data received from the environmentalmonitoring module 118.

The display module 116 is coupled to the display device 82 to receivefrom and display information to the operator via the display device 82.The display module 116 also receives signals indicative of a user'sselection and transmits the data to the flow distribution module 110,the cargo access module, the venting control module 114, and theenvironmental monitoring module 118. The display module 116 alsogenerates audible and visible alarms to provide a notification to theuser of an environmental condition of the cargo trailer 14.

The environmental monitoring module 118 receives data indicative ofenvironmental parameters from the sensors 78 and determines anenvironmental condition of the cargo trailer 14 as a function of thereceived environmental parameters. In addition, the environmentalmonitoring module 118 also receives data indicative of the operation ofthe fluid distribution assembly 16, the ventilation assembly 18, and thecargo access assembly 20, and transmits data to the flow distributionmodule 110, a cargo access module 112, and a venting control module 114to control an operation of the fluid distribution assembly 16, theventilation assembly 18, and the cargo access assembly 20, respectively.

In the illustrated embodiment, during operation of the system 10, thecontroller 80 is configured to receive a monitoring signal indicative ofthe sensed environmental parameter from at least one sensor 78 anddetermine an environmental condition of the cargo trailer 14 as afunction of the environmental parameter. The controller 80 is alsoconfigured to provide a notification signal via the display device 82 ifthe determined environmental condition is different than a predefinedenvironmental condition. For example, in one embodiment, the controller80 may receive a request from the operator to access the interior volume12, responsively determine an environmental condition of the interiorvolume 12, and provide a notification to the operator indicative of thedetermined environmental condition. By providing a notification to theoperator of the environmental condition of the interior volume 12, thesystem 10 may notify the operator of any potentially hazardous areaswithin the interior volume 12 before the operator enters the area.

In one embodiment, the controller 80 receives a signal from an oxygensensor 86 that is indicative of a level of oxygen within the interiorvolume 12. The controller 80 may determine the environmental conditionas a function of the sensed oxygen level.

In addition, in the illustrated embodiment, the controller 80 isconfigured to receive a request to adjust a temperature within the cargointerior volume 12 and operate the fluid distribution assembly 16 toadjust the interior volume temperature if the determined environmentalcondition is equal to the predefined environmental condition. Forexample, the environmental monitoring module 118 may receive a requestfrom the flow distribution module 110 to operate the fluid distributionassembly 16 to lower a temperature within the interior volume 12. Theenvironmental monitoring module 118 determines an environmentalcondition based on the sensed environmental parameters and operates thefluid distribution assembly 16 based on the determined environmentalcondition. In one embodiment, the controller 80 may receive a request tooperate the fluid distribution assembly 16, responsively senses amovement within the interior volume 12 to determine a presence of anoperator/user within the interior volume 12 as a function of the sensedmovement, and operates the fluid distribution assembly 16 upondetermining the operator is not within the interior volume 12. Inaddition, the controller 80 may also determine an operating condition ofthe cargo access assembly 20, and operate the fluid distributionassembly 16 if the determined operating function is equal to apredefined operating function. For example, the controller 80 maydetermine if the cargo access assembly 20 is in the locked position toprevent access to the interior volume 12 and operate the fluiddistribution assembly 16 only if the cargo access assembly 20 is locked.

In another embodiment, the controller 80 may receive a request from anoperator to operate the cargo access assembly 20 to provide access tothe interior volume 12. The controller 80 may determined whether thesensed interior volume environmental condition is equal to thepredefined condition and operate the cargo access assembly 20 to enablean operator to enter the interior volume 12 if the determinedenvironmental condition is equal to the predefined environmentalcondition. For example, the controller 80 may determined if sensedoxygen levels are within predefined oxygen levels before operating thecargo access assembly 20 to ensure the interior volume 12 includessufficient amounts of breathable air. In addition, the controller 80 maydetermine if the ambient temperature within the interior volume 12 isabove a predefined temperature before operating the cargo accessassembly 20 to ensure the interior volume is at a temperature that issafe for entry. In addition, the controller 80 may provide anotification of the oxygen levels and/or ambient temperature of theinterior volume 12 to the operator before operating the cargo accessassembly 20. In addition, the controller 80 may continuously monitor theinterior volume 12 with the cargo access assembly 20 in the unlockedposition and provide notification to the operator of a change in one ormore environmental parameters such as a change in temperature and/or achange in oxygen levels.

In one embodiment, the controller 80 may also operate the ventilationassembly 18 as a function of the determined environmental condition. Forexample, the controller 80 may receive an operator request to access theinterior volume 12 and responsively operate the ventilation assembly 18upon receiving the request. In addition, the controller 80 may operatethe ventilation assembly 18 upon sensing the cargo access door 40 and/orthe cargo access assembly being unlocked.

In the illustrated embodiment, the controller 80 is configured tomonitor on operation of the fluid distribution assembly 16. Moreover,the controller 80 is configured to receive, from one or more sensor 78,a monitoring signal indicative of an operating parameter of the fluiddistribution assembly 16 and determine an operating condition of thefluid distribution assembly 16 as a function of the sensed operatingparameter. In one embodiment, the controller may also provide anotification signal if the determined operating condition is differentthan a predefined operating condition. For example, the controller 80may receive a signal indicative of a temperature of the cryogenic fluidbeing discharged from at least one spray nozzle assembly 54 and providea notification if the sensed temperature is different than a predefinetemperature. In addition, the controller 80 may receive a signalindicative of a sensed temperature of the fluid conduit 56, a senseddifferential pressure across at least one control valve 58, and/or asensed fluid pressure within the fluid distribution assembly 16 andprovide a notification to the operator if the sensed parameters aredifferent than predefined operating parameters.

In the illustrated embodiment, the controller 80 may also receive asignal indicative of an ambient temperate within the interior volume 12,and operate the fluid distribution assembly 16 to selectively channelthe cryogenic fluid 50 into the interior volume 12 as a function of thesensed temperature. In one embodiment, the controller 80 determines aflow rate of the cryogenic fluid 50 being channeled into the interiorvolume 12 as a function of a predefined rate of cooling and the sensedinterior temperature, and channels a flow of cryogenic fluid 50 into theinterior volume 12 at the determined flow rate. The controller 80 alsodetermines an actual rate of cooling as a function of the sensedinterior temperature monitored over a predefined period of time, andadjusts the flow rate of cryogenic fluid 50 being channeled into theinterior volume 12 to reduce a difference between the actual rate ofcooling and the predefined rate of cooling. In one embodiment, thecontroller 80 determines a flow rate of cryogenic fluid 50 as a functionof a sensed interior temperature, an exterior trailer temperature,and/or an insulation value of the cargo trailer 14.

In the illustrated embodiment, the controller 80 is also configured todetermine an environmental condition associated with each of theplurality of zones 44 defined within the interior volume 12 and providea notification signal indicative of the determined environmentalcondition of each one of the zones 44. The controller 80 is alsoconfigured to sense a temperature within each of the zones 44 andoperate the fluid distribution assembly 16 to selectively channel a flowof cryogenic fluid 50 to each one of the zones 44 to adjust atemperature of the zones 44 independently.

FIG. 8 is a flowchart of a method 200 that may be used with the system10 for controlling a temperature within the interior volume 12 of thecargo trailer 14, according to an embodiment of the invention. Eachmethod step may be performed independently of, or in combination with,other method steps. Portions of the method 200 may be performed by anyone of, or any combination of, the components of the system 10. In theillustrated embodiment, the method 200 includes the steps of receiving202 a monitoring signal indicative of a sensed environmental parameter,determining 204, by the system 10, an environmental condition of thecargo trailer as a function of the sensed environmental parameter, andproviding 206 a notification signal to an operator if the determinedenvironmental condition is different than a predefined environmentalcondition. The system 10 may also determine an environmental conditionassociated with each one of a plurality of monitoring zones definedwithin the interior volume and provide a notification signal to theoperator indicative of the determined environmental condition of eachone of the monitoring zones.

In the illustrated embodiment, the method 200 also includes the step ofreceiving 208 a signal indicative of a sensed level of oxygen within theinterior volume and determining the environmental condition as afunction of the sensed oxygen level. In addition, the method includesthe steps of receiving 210 a request to adjust a temperature within thecargo interior volume and operating 212 the fluid distribution assemblyto adjust the interior volume temperature if the determinedenvironmental condition is equal to the predefined environmentalcondition.

The method 200 also includes the step of determining 214 a presence ofan operator within the interior volume as a function of the sensedmovement and operating the fluid distribution assembly upon determiningthe operator is not within the interior volume. In addition the method200 may include the step of determining 216 an operating condition ofthe cargo access assembly and operating the fluid distribution assemblyif the determined operating function is equal to a predefined operatingfunction. The method 200 may also include the steps of receiving 218 arequest to access the interior volume and responsively operating thecargo access assembly to enable an operator to enter the interior volumeif the determined environmental condition is equal to the predefinedenvironmental condition. The system 10 may also receive a request toaccess the interior volume and responsively operating the ventilationassembly upon receiving the request.

The method 200 may also include the steps of determining 220 anoperating condition of the fluid distribution assembly as a function ofthe operating parameter and providing a notification signal if thedetermined operating condition is different than a predefined operatingcondition. In addition, the system 10 may also receive a signalindicative of an ambient temperate within the interior volume andoperate the fluid distribution assembly to selectively channel cryogenicfluid into the interior volume as a function of the sensed temperature.The system 10 may also determine a flow rate of cryogenic fluid beingchanneled into the interior volume as a function of a predefined rate ofcooling and a sensed interior temperature; channel a flow of cryogenicfluid into the interior volume at the determined flow rate; determine anactual rate of cooling as a function of the sensed interior temperaturemonitored over a predefined period of time, and adjust the flow rate ofcryogenic fluid being channeled into the interior volume to reduce adifference between the actual rate of cooling and the predefined rate ofcooling. The system 10 may also determine a flow rate of cryogenic fluidas a function of one of the sensed interior temperature, an exteriortrailer temperature, an insulation value of the cargo trailer.

Referring again to FIGS. 1-7, in one embodiment, the system 10 mayinclude a semi trailer cargo temperature control unit that includes ameans by which to dispense liquid nitrogen (LN₂) into the cargo hold ofa semi trailer for the purpose of cooling cargo, an electronic controlsystem by which to modulate the flow rate of LN₂ to maintain thetemperature at a user-defined setpoint, a safety system to measure oneor more environmental conditions in the cargo hold and provide audibleand/or visible warning to the operator, a safety system to measure oneor more environmental conditions in the cargo hold and guard theoperator from potentially hazardous conditions, a method for ventilatingfresh air into the cargo hold, using an air supply from one or morecargo door(s) and ducting to direct the airflow, a human/machineinterface (HMI) to provide the operator with a means to issue systemcommands and receive information on the system behavior, and aself-contained electrical energy storage system to allow operation ofthe cooling system when not connected to a tractor or a stationary powersource. The system 10 may also include a cargo temperature control unitcomprising the elements described adapted for use on a “straight truck”.

The system 10 may also include a system which incorporates one or moremethods by which to divide the cargo hold into two or more zones, eachzone with the ability to maintain its temperature independently ofadjacent zones, and which incorporates individual controls and setpointsfor each sprayer outlet.

The system 10 may also include a safety system that includes at leasttwo independent oxygen measurement devices, with a means by which tocompare the output of each device to one another for the purpose ofproviding diagnostic checks, a means to communicate the oxygen level ofthe cargo to the user, a microprocessor-based control subsystem for thewarning function, a discrete electronic control subsystem for theguarding function, in which no software is utilized, a means by which tocompare the calculated state of the warn subsystem and guard subsystem,and to prevent operator entry if the states do not agree, a discreteelectromechanical or electronic interlock between the emergency stop(“E-stop”) button and cryogenic valves that causes the valve power to beinterrupted upon emergency stop activation, an emergency stop buttonmechanism that provides an electrical command to various system elementsvia a discrete signal and/or a serial communication bus, a discreteelectromechanical or electronic interlock between the guarding mechanismand cryogenic valves that causes the valve power to be interruptedwhenever the guard mechanism is not locked into place, and a guardingmechanism that provides an electrical command to various system elementsvia a discrete signal and/or a serial communication bus.

In one embodiment, the system 10 may include a safety system for acryogenic cargo cooling unit as described above that utilizes three ormore oxygen measurement devices and a majority voting technique in orderto provide continuous operation with the failure of one or more sensors,and a safety system for a cryogenic cargo cooling unit as describedabove that utilizes redundant and independent means of communicatinginformation about oxygen levels to the warning and guarding subsystems.In addition, the system 10 may include a safety system for a cryogeniccargo cooling unit as described above where the redundant andindependent means includes a serial communication bus and a hardwireddiscrete signal line, and a safety system for a cryogenic cargo coolingunit as described above that provides one or more of the following meansby which to detect a cryogenic valve that is malfunctioning in a mannerthat allows LN₂ to enter the cargo hold, and provides the appropriatewarning to the operator.

In another embodiment, the system 10 may include a means by which tomeasure temperature in the cryogenic line downstream of the valve, ameans by which to measure differential pressure across the valve, and ameans by which to measure the discharge temperature of the sprayernozzle in the cargo hold.

The system 10 may also include a safety system that utilizes analternative discharge opening outside the cargo area and a valve tocontrol the opening for the purpose of safety discharging nitrogenoutside the cargo area in event of a malfunctioning cryogenic valve.

In addition, the system 10 may also include the use of one or more meansby which to detect that a person is occupying the cargo hold, and toinhibit the injection of LN₂ while the cargo hold is inhabited includingthe use of passive infrared sensing with one or more zones of detection,the use of active infrared sensing, the use of automated opticaldetection using wavelengths in the visible or infrared range, and theuse of radio frequency detection and ranging techniques.

The system 10 may also include a safety system for a cryogenic cargocooling unit that provides a means by which to alert users at the entryto the trailer of a safety-related fault or error, visual warning beaconalong the inside perimeter of the trailer door frame, and audiblewarning siren mounted to the outside entry of the trailer in such amanner as to be audible from inside a typical shipping facility (or“dock”). The system 10 may also include a safety system for a cryogeniccargo cooling unit that requires a particular sequences of events priorto releasing nitrogen into the cargo hold, including the manipulation ofmore than one switch in the interior or exterior of the cargo hold insuch a manner that requires the operator to inspect the cargo hold forthe presence of other occupants. This may also include a requirementthat the manipulation events occur within a specified period of time.

In one embodiment, the system 10 may also include a cryogenic coolingsystem for the transportation of refrigerated or frozen goods thatutilizes a combination of feed-forward and feedback control techniquesto regulate the cargo temperature, a controller that utilizes infraredsensors or cameras to determine the temperature of the cargo hold andits contents for the purpose of providing a feedback signal, acontroller that utilizes an estimation of the liquid nitrogen flow rateto estimate the current rate of cooling, including the use of measuringthe pressure differential between the vessel and cargo hold, acontroller that utilizes temperature information from the interior andexterior of the cargo hold, as well as an estimate of the cargo holdinsulation value, to estimate the current rate of heating, a controllerthat utilizes estimates of the rate of heating to form a feed-forwardcommand to the cooling system, and a controller that utilizestemperature feedback to modify its estimate of cargo hold insulationvalue.

The system 10 may also include a cargo temperature control system thatutilizes temperature measurement located within or near cargo hold vents(example: floor drains) to obtain information about the condition(temperature) of the gases exiting the trailer for the purpose ofoptimizing energy consumption. In addition, the system 10 may alsoinclude a means by which the physical location of zone-specific modulesin a multi-zone system can be automatically determined by the coolingsystem, a hardware solution using discrete connections in the wiringharness to provide a location-specific configuration of multipleconnector pins, and a software solution using system stimulus and modulebehavior to determine the location of one or more modules.

In one embodiment, the system 10 may also include a cryogenic cargotemperature control system that utilizes multiple serial communicationbuses, including at least one which is dedicated to communication onlyamong the cooling system control modules (“private”), and at least onewhich is dedicated to communication between the cooling system andexternal accessories such as data acquisition and telematics equipment(“public”). In addition, the system 10 may also include an oxygenmeasurement system as described above that utilizes integratedmeasurement of barometric pressure or the estimation of barometricpressure via means such as global positioning system (GPS) to providepartial-pressure compensation for varying atmospheric conditions. Inaddition, the system 10 may also include an oxygen measurement system asdescribed above that utilized the cargo temperature measurementtechnique to provide partial-pressure compensation for varyingatmospheric conditions.

In one embodiment, the system 10 may also include a liquid nitrogendistribution system as described above that utilized an integrated valvebody or manifold to route liquid nitrogen from the cryogenic vessel headthrough the flow control valves to one or more independent zones(s), andan integrated valve body that additionally integrates one or moremeasurement means to detect a malfunctioning cryogenic valve. Inaddition, the system 10 may also include a safety system that utilizesone or more methods of measuring cargo hold air pressure (including theuse of the barometric pressure sensors) to provide a warning to theoperator that the cargo hold has become pressurized above atmosphericlevels, a liquid level measurement system that utilizes a device tomeasure the inclination of the vessel, and also the differentialpressure of the vessel to determine the appropriate “level” measurementof the vessel, and a liquid level measurement system that utilizes amulti-axis accelerometer as the device to measure the inclination of thevessel.

In another embodiment, the system 10 may also include a cargo holdconstructed with one or more remote-operated valves that can be openedwhen the system is not operating for the purposes of cleaning andservicing the trailer, but are closed during normal cooling modes toimprove the insulation performance of the cargo hold, and a means bywhich to allow ambient air into the trailer if the ambient airtemperature is below the temperature inside the cargo hold, and a meansby which to close this entry upon the cargo hold temperature reachingthat of the ambient air temperature.

In addition, the system 10 may also include a means to create a multizone trailer utilizing a multitude of safety locking devices (guardsections) installed along the length of the trailer at an interval thatmatches the length of a standard pallet for the purpose of allowing anoperator to install a removable bulkhead in a multitude of locationsaccording to the cargo composition, and a system utilizing a means ofzoning described in claim 27 wherein the temperature control systemutilizes information about the removable bulkhead position to establishappropriate cooling tuning parameters according to the enclosed volumeof the cargo hold zone. In one embodiment, the system 10 may alsoinclude a means to create a multi zone trailer utilizing a multitude ofdiscrete plug in locations for a singular safety guarding device toallow the operator to install a removable bulkhead in a multitude oflocations and a means to implement a removable bulkhead where one sideis mechanically latched into the side wall, and the opposite side isheld in place via an electromechanical safety locking device.

In one embodiment, the system 10 may also include a method to evacuatethe air in the cargo area using a flexible closure device held in placewith magnetic strips and which automatically opens and closes accordingto circulation fan operation. In addition, the system 10 may alsoinclude a filling station that utilizes information about the vehicleposition and a means of communication with the cooling system toautomatically put the system in fill mode when pulled up to the fillingstation, where the means of vehicle position is provided via globalpositioning system (GPS) and the means of communication is a wirelessformat such as Bluetooth or WiFi, a cooling system that utilizinginformation about the vehicle position to automatically engage in theventilation process when a vehicle reaches its destination, and acooling system that utilizes a global positioning system (GPS) to form avirtual “geo-fence” in order to determine the location of a destinationand to automatically initiate ventilation of the cargo hold.

In another embodiment, the system 10 may also include a cryogeniccooling system that uses a means to detect the rotation and/or rapiddeceleration of the vehicle to detect a potentially hazardous collisionor rollover event for the purpose of automatically operating the ventvalve in order to reduce the stored mechanical energy in the storagevessel and a cryogenic cooling system that utilizes a collisiondetection function that utilizes any combination of multi-axisaccelerometers and gyroscopic yaw sensors to detect a collision orrollover event. In addition, the system 10 may also include a means bywhich to power an electromechanical latching mechanism on a removablebulkhead by applying a voltage potential between the load securingmechanisms (“E tracks”) on opposite sides of the trailer and a means bywhich to power an electromechanical latching mechanism on a removablebulkhead by locating an electrochemical storage battery in the bulkhead.

In another embodiment, the system 10 may also include a device toprotect the rollup door and warn the operator of conditions within thetrailer, ODP barrier light tower, a guarding mechanism that can bestored in a closeable “locker” built into the side wall to keep it outof the way of the load unload process, and a mounting method for a doorswitch to protect it and allow visibility.

Purpose and Functionality

The system 10 described herein may include a direct LN₂ cryogeniccooling system (CCS) for insulated cargo trailers. This includes theelectronic and mechanical elements required to maintain operator safetyand control the temperature of the cargo. Additional elements will beprovided to interface with the user for the purpose of communicatinginformation about the operation of the cooling system, setting theoperational mode, and allowing system maintenance.

It is acknowledged that the inherent design, operation, and maintenanceof a system that utilizes the direct injection technique also may exposeoperators to a variety of hazards. Safety countermeasures will bedeveloped to reduce the risk of operator hazard to an acceptably lowlevel.

System Interfaces: the following is a list of interfaces between theitem and its surrounding environment.

Trailer body/chassis—the system will be installed into a trailer that isconstructed by the vehicle manufacturer. This includes the trailer roof,sidewalls, floor, and frame. The trailer cargo compartment provides aninsulated environment for the cargo, as well as paths for running cablesand piping. Various system elements rely on the trailer body and chassisto provide mechanical mounting locations.

Tractor umbilical(s)—the item will be connected to the tractor via astandard 7-way connection, and additionally may utilize dedicated powerand data connections. Via the connections to the tractor, the trailerwill receive +12V power, ground, and the brake signal, as well as anyother signals that may be required for ancillary functions (such astelematics and data acquisition). The +12V power supply will allowcharging of the system batteries when the trailer is connected to atractor. The brake signal may be utilized to reduce current draw fromthe +12V supply during braking events, as the trailer antilock brakingsystem (ABS) may need to draw significant current from this line.

Solar panel—the item may draw power from a solar panel mounted on thetrailer roof. The purpose of this supply is to maintain battery chargelevel when the trailer is not connected to a tractor or to shore power.

Shore power—the item may draw power from an 110V/220V supply whenplugged into a stationary source of “shore power”. This will allowcharging of the system batteries.

Batteries—the item will draw upon one or more chemical storagebatteries, located on the trailer body or chassis. The nominal voltageof this supply is 12V. The system is presently intended to make use oflead-acid battery chemistry, although other battery technology may beemployed in future versions as advanced technology becomes moreeconomical.

Filling port—the item will be connected to a filling port that allows anoperator to refill the LN2 vessel.

Thermal interface—the vessel will receive heat from its environment forthe purpose of building internal pressure via the phase change of storednitrogen from liquid to vapor. This pressure will drive the LN2 throughthe valves, plumbing, and sprayer bars. The trailer body will alsoreceive thermal energy from the environment, with the potential effectof changing the thermal load presented to the TRU.

Vessel venting—The vessel will vent excess N2 vapor to its surroundingenvironment in order to maintain a safe system pressure.

LN₂ distribution—The item will dispense nitrogen (as a liquid, vapor, ormixed-phase flow) into the cargo hold.

Information—the system provides information to operators via visual andaudible means.

Elements of the Item

LN₂ storage vessel. This is a double-wall vacuum-insulated containerthat is constructed of stainless-steel components. The vessel containsmeans by which to build and regulate its internal pressure. The LN2vessel will also contain a means by which to measure fuel level.

Valve assembly. Co-located with the vessel is a system of valves thatregulate the flow of LN2 from the vessel for the purpose of cooling,venting, and fueling. Electromechanical valves are utilized forfunctions under direct command of the item's electronic control system,while manual valves may be utilized for the purpose of maintenance,repair, and emergency response.

Sprayer assemblies. One or more sprayer assemblies (“spray bars”) willbe utilized to provide nitrogen to the cargo hold. These devices areconstructed of aluminum extrusions or fabricated structure, and containdesign features to quickly evaporate the liquid nitrogen into itsgaseous form as it is sprayed into the cargo hold.

Plumbing. Metallic or composite pipes will be provided to facilitate thetransfer of LN₂ from the vessel to the sprayer assembly. Typicallyrouting of this plumbing would be along the trailer underbody, throughthe trailer walls, and within the trailer interior. The plumbing must becapable of withstanding the thermal loads provided by the LN₂ containedwithin, as well as being compatible with the trailer manufacturingprocess.

Ventilation fans. Located near the sprayer bars, the ventilation fansare tasked with circulating fresh air into the cargo compartment inorder to return the oxygen concentration to a level that is safe foroperators.

External Control Panel (ECP). This module presents an HMI to theoperator via an electronic display (such as an LCD panel), andcommunicates user requests to the cooling system. An operator will beable to program the system operating mode, program setpoints related tothe cooling parameters, and receive information about the system'soperation. System diagnostic information will also be available for thepurpose of troubleshooting and repair. A data interface (such as a USBconnection) will be provided to allow for data retrieval andreprogramming of module software.

Oxygen Display Panel (ODP). This electronic control unit presents aninterface to the user for the purpose of communicating informationrelated to the oxygen level in the cargo hold. The ODP also contains theelectronics and mechanisms for the gate locking device.

Power Control Unit (PCU). This electronic control unit is tasked withmanaging the various power supply sources to the system for the purposeof maintain proper battery state-of-charge (SOC), providing otherelectronic control units with power from the system batteries,controlling the electromechanical valves, CAN bus monitoring, and makingoperation decisions based upon sensor data and user commands.

Spray Nozzle Unit (SNU). This is an electronic control unit that obtainsdata from the temperature sensors, and actuates the fans during theventilation cycle. This module is located near one of the spraybarassemblies.

Driver Light Panel (DLP). This module employs a series of LED indicatorlamps that are placed as to be visible in the driver's rear-viewmirrors. Information about the system operating status can becommunicated using a combination of LED behaviors (color, blinking vs.solid illumination, various combinations of lamps illuminated, etc.).

O2M. This module acquires data from a set of oxygen sensors, performscompensation, filtering and diagnostics, and communicates the calculatedvalue via the CAN bus and a discrete signal line to the ODP.

Oxygen sensors. Oxygen sensors will be utilized to measure the actualoxygen content of the air contained within the cargo hold. The sensoroutput may require compensation for ambient temperature and barometricpressure, and will typically require re-calibration at several points inthe sensors' lifespan. These sensors require warm-up time at thebeginning of each power cycle in order to stabilize at a controlledtemperature.

Temperature sensors. Each zone will have temperature sensors to measurethe temperature of the cargo hold. Additional sensors may be provided tomeasure the temperature near the sprayer bar outlet for verification ofproper LN₂ flow. The external temperature may also be measured forpurposes of establishing proper cooling function.

Barometric pressure sensor—in order to compensate the O2 sensors forvarying ambient pressure, as well as providing additional information onLN₂ flow rate, a barometric pressure sensor may be utilized.

CAN bus. Modules within the system will be connected via controller areanetwork (CAN) in order to communicate data and commands.

Door sensor. The door sensor is used measure the status of the cargodoor.

E-stop. The emergency stop—or E-stop—button is used to immediately haltLN₂ dispensing and active an external alarm if a human is present duringthe cooling cycle operation.

Safety lock solenoid. The safety lock solenoid is an electromechanicaldevice that, when commanded by a module within the ODP, releases thesafety locking member and allows entry to the cargo hold. It containsmultiple sets of mechanical switch contacts to determine the status ofthe locking member.

Operation. The system is placed into cooling mode with an operatorcommand via the ECP HMI. If a series of self-tests are passed, and thecargo door is closed and the gate locking device properly secured, thesystem will initiate cooling operation. Temperature setpoints as well asdesired cooling ramp rates and pre-set profiles, can be commanded by theoperator via the ECP. If the cooling function is inhibited due to anynumber of possible reasons, the ECP will attempt to communicate thisinformation to the operator for the purpose of debugging or service.

The cooling function consists of dispersing LN2 into the cargo hold tomaintain the programmed temperature set point. In this operational mode,the valve duty cycle will be varied in order to provide the volume ofnitrogen required to provide sufficient energy to cool the cargo andcompensate for heat loss through the trailer walls. Both feedback andfeed-forward techniques may be employed to determine the valve dutycycle, and models of the trailer and cooling system performance may beutilized to further serve this purpose. In the case of multiple zones,the appropriate information will be used to independently control thetemperature of each zone.

Upon opening the cargo door, dispensing of LN2 will cease, and theventilation fans will circulate fresh air through the cargo door andinto the cargo hold if the oxygen levels are below the minimum safethreshold. Until the cargo hold oxygen levels are determined to be abovethe minimum safe threshold, the ODP will indicate via audible and visualwarnings that a potentially unsafe O2 level is present, and the gatelock will not release upon request. Ventilation will continue untilsufficient air is exchanged with the environment. Once the O2 levelreturns to a safe state, the ventilation fans will cease operation, theODP will indicate that a safe O2 level has been reached, and the gatelock will release upon operator command.

The cooling function can be re-initiated by once again securing thecable gate lock and closing the cargo door.

Oxygen levels may be monitored continuously during normal operation ofthe cooling system.

Refueling. The refueling functional mode facilitates operation of theCCS by replenishing the level of LN2. This mode can be accessed duringthe storage or cooling modes by activating a momentary switch near theLN2 refueling port, and connecting a fuel source (typically acustom-installed fueling station, although refueling from a mobile truckmay be required during development or service).

During fueling, the operator will be tasked with making the physicalconnection between the fuel source and the CCS, monitoring the progressof the fueling process, disconnecting the station upon cessation offueling, and recording metrics related to the CCS operation (typicallyrelated to the time of operation and the volume of fuel consumed).

Storage. In storage mode, the goal is to minimize the power consumptionof a trailer that is not being used for some period of time (typicallycharacterized as days or weeks of downtime). In this mode of operation,the trailer should be placed into a safe state, and all systems notrequired for maintaining a safe state shall be powered-down until thesystem is commanded into a different functional mode.

Maintenance/Service. Maintenance/service mode will be used to retrieveany current or stored diagnostic trouble codes (DTCs) and assess theperformance of the system or elements of the system. It can be assumedthat a maintenance technician may, at a minimum, need to access sensordata and manually activate loads such as the ventilations fans, warningdevices, and valves.

Foreseeable misuse. The following situations should be considered in thedesign and deployment of the CCS:

Person seeking cool environment. Operators or bystanders often willutilize a refrigerated trailer for personal comfort, particularly inwarmer climates. With existing diesel TRUs, this presents minimal hazardto the operator. In a cryogenic direct-injection system, a personutilizing the system in this fashion is likely to be exposed to anenvironment depleted of O2.

Overfilling. It is possible that an operator may seek to deliberatelyoverfill the system in an attempt to gain more usable range.

Auxiliary Refrigeration. An operator may seek to use the CCS tosupplement or relieve the HVAC system of the building to which thetrailer is docked. An example of this scenario would be an attempt touse the trailer's cooling system in case of a power outage at adistribution center or grocery store. Such usage could result increating an environment that is depleted of O2.

Summary of Safety Goals—the following list is a summary of safety goalswhich must be satisfied to avoid unacceptable risk of exposing a user ofthe system to one or more hazards. The operator must be protectedagainst entering a cargo hold that is depleted of O2. The system mustnot allow the cargo hold to become depleted of O2 while an operator ispresent. The operator must be provided a means by which to inhibit therelease of LN2. The system must not allow the rapid release ofmechanical energy from the vessel during normal use. The system must notallow the rapid release of mechanical energy from the vessel duringtraffic accidents. The rapid release of mechanical energy from the cargohold must be avoided during normal operation.

For the scenario in which an operator may enter a cargo hold that isdepleted of O2, a CCS without any safety features would depend upon anoperator's ability to determine whether the cargo hold is safe to enter.As the effects of O2 deficiency may incapacitate the operator, and mayarise without warning, this is clearly not a workable solution for evenhighly-trained operators. Additional safety mechanisms are determined tobe required to prevent an operator from entering a cargo hold that isdepleted of O2.

For scenarios involving the discharge of LN2 into an occupied cargo holdthat was previously at a safe O2 level, it may be reasonable to expectthat the operator will notice the effects of O2 deficiency in theabsence of other distractions. Given the typical working environmentwith a substantial amount of activity in and around the trailer, it isunreasonable to solely rely upon the user to avoid this hazard.Additional safety mechanisms are determined to be required to preventthe discharge of LN2 into an occupied cargo hold that was previously ata safe O2 level.

For scenarios involving the discharge of LN2 into an occupied cargo holdwith a locked door, the operator may not be able to locate the doorlatch mechanism and correctly manipulate it within the fault toleranttime interval. The result would be that the operator may be exposed toan environment depleted of O2. Additional safety mechanisms aredetermined to be required to the discharge of LN2 into an occupied cargohold with a locked door.

The scenario associated with the release of mechanical energy from thecargo hold during door opening may be addressed via non-E/E means.Ventilation of the cargo hold can prevent the accumulation of N2 and thesubsequent rise in pressure. For trailers with outward-swing doors,labeling can be provided near the cargo hold door latch to warn anoperator of this hazard and instruct the operator to stand clear of thedoor during unlatching. No additional safety mechanisms are determinedto be required if the described non-E/E measures are implemented.

Potential Safety Mechanisms

O2 Monitoring. It is possible to monitor the O2 levels of the cargo holdduring times where it is reasonable to expect that an operator may bepresent, or may wish to enter the hold. This technology iscommercially-available at a reasonable cost. Information concerning the02 levels can be transmitted via the serial bus or discrete signalpaths. These techniques may use electrical or optical signals. Thepractice of monitoring O2 levels is not itself a complete safetymechanism, as there is also the need to provide information to anoperator, or take action against a potentially unsafe operator activity.

Valve Monitoring. By monitoring the status of the cryogenic controlvalves, it is possible to determine if the environment is at risk ofbecoming unsafe to an occupant. Multiple monitoring techniques arepotentially feasible, as described below. The direct monitoring of valvepintle position may be possible. This technique would allow the systemto determine if a valve is being driven to an open position, or if thevalve is being held open by a mechanical issue even when unpowered.Pintle position monitoring for cryogenic valves is not widely available.The direct monitoring of the valve electrical power supply is possible.This should allow an ECU to determine if power is inadvertently beingapplied to the valve and thus allowing an unintended discharge of LN2.It does not address mechanical issues that may cause LN2 discharge.Electrical monitoring of the valve electrical power supply is readilyaccomplished through typical ECU diagnostic techniques. The valves mayalso be monitored indirectly by the measurement of temperature or O2levels. Temperature can be measured downstream of the valve (either inthe distribution plumbing, or via a temperature probe placed near thespray bar discharge location). A significant drop in temperature whenthe system should not be actively cooling could indicate anunintentional discharge of LN2. Additionally, unintended release of LN2may be inferred by a drop in O2 levels when the system should not beactively cooling the cargo hold. Information concerning the valveoperation can be transmitted via the serial bus or discrete signalpaths. These techniques may use electrical or optical signals. Thepractice of monitoring O2 levels is not itself a complete safetymechanism, as there is also the need to provide information to anoperator, or take action against a potentially unsafe operator activity.

Occupant Detection. It is possible to monitor the cargo hold for thepresence of an operator. Technologies include passive detection systemsthat utilize signals in the visible-light or infrared spectrums, as wellas active detection systems using ultrasonic or laser emitters anddetectors. As the cargo is generally stationary and typically muchcolder than the human body, it should be possible to determine if anoperator is present if that person is moving. Potential drawbacksinclude false triggering due to cargo movement, as well as thepossibility of cargo obstructing the mechanism's ability to “see” anoccupant. An E-stop switch may be considered to be a means of occupantdetection. This would depend upon the operator's ability to perceivethat unsafe conditions potentially exist. Detection of the cargo doorcan be considered to be a means of occupant detection during normaloperation of the system, as the cargo hold can be assumed to be occupiedif the door is open. Making the opposite assumption (that the cargo holdis unoccupied if the door is closed) would rely on operator inspectionof the hold prior to closing the door. Information concerning theoccupant status can be transmitted via the serial bus or discrete signalpaths. These techniques may use electrical or optical signals. Thepractice of detecting an occupant is not itself a complete safetymechanism, as there is also the need to provide information to anoperator, or take action against a potentially unsafe operator activity.

Warning of Unsafe O2. With some combination of O2 monitoring, valvemonitoring, and occupant detection in place, sufficient information isavailable to provide a warning to an operator that the environment iseither unsafe, or at risk of becoming unsafe. A warning may take theform of active audible or visual indications, as well as labels andplacards. Audible warnings, such as alarms, could provide an effectivewarning for operators who have an obstructed line of sight to a visualwarning, or have vision problems that may prevent the properinterpretation of a visual warning. Such an alarm would need to have anappropriate sound pressure level (SPL) to attract the attention of theoperator, but not so loud as to form an annoyance or health hazard toadjacent workers. The frequency of the alarm should be established as toallow an operator to determine the location of the emitter, for theremay be several trailers in the vicinity. Visual warnings such as lampsand numerical displays may be employed to give the operator informationabout the cargo hold environment. A simple indicator can be used to showwhether the hold is safe or unsafe; such an indicator should use bothcolor (red and green, for example) and position (the two colors ofindicator should not share the same location) to allow a user withnormal visual acuity or one with color deficiency to properly interpretthe warning. Alphanumerical information can also be presented to theoperator, although training may be required to properly interpret thedata. Although not an E/E safety mechanism, labels and placards can bean effective means of informing an operator of potential hazards.Information concerning the warning function can be transmitted via theserial bus or discrete signal paths. These techniques may use electricalor optical signals. False warnings should be avoided, as they can leadto operators disregarding the information provided by the system and aresultant degradation of the effectiveness of this mechanism.

Guarding against Unsafe O2. With some combination of O2 monitoring,valve monitoring, and occupant detection in place, it is possible toprovide a guard to prevent an operator from entering an environment thatis potentially unsafe. One form of a guard consists of acommercially-available electromagnetic actuator in combination with acable (or alternatively, a fabric net). The cable is strung across thecargo hold entrance, with one end anchored to the cargo hold structureand the other end secured by the actuator. When unpowered, the actuatorprevents the release of the cable and thus does not allow the entry of aproperly-trained operator. The system will power the solenoid to releasethe cable only when the cargo hold door is open, measured O2 levels aredeemed safe, and the nitrogen solenoid valves are unpowered anddetermined to be closed. A standard mechanical door lock can also serveas a form of a manually-operated guard. The guard must be constructed insuch a manner as to allow a trapped operator to leave the cargo hold ifnecessary. This may be accomplished via the mechanical design of theguard device, or electronically releasing the guarding device uponactivation of the E-stop or occupant detection device. If this task isaccomplished via E/E means, then the function must be provided via asystem with the appropriate ASIL. Information concerning the guardingfunction can be transmitted via the serial bus or discrete signal paths.These techniques may use electrical or optical signals. Improperoperation should be avoided, as they can lead to operators disregardingthe safety function provided by the system and a resultant degradationof the effectiveness of this mechanism.

Inhibiting Release of LN2. A system mechanism that inhibits LN2 releasemay be implemented by ensuring that the electromechanical solenoidvalves are not powered. To ensure that this is the case, multiplesources of high-side and low-side power may be utilized to provideadditional assurance that the valve has not become inadvertentlypowered. The release of LN2 may also be inhibited by a manual valve. Inthis case, operator intervention would be required in order to activatethe safety mechanism. A manually-actuated mechanism by which to inhibitthe release of LN2 by deactivating the system may be utilized to allow atrapped operator to avoid harm. This mechanism should be easilymanipulated (such as a large pushbutton as typically employed byemergency stop switches), and should be backlit to allow a user toquickly locate it in a darkened trailer. A luminous (“glow-in-the-dark”)label can assist in locating the E-stop switch.

Safety mechanisms. While the system is capable of creating anenvironment that is potentially depleted of O2, the oxygen levels may beperiodically monitored within the fault tolerant safety interval.

The O2 monitoring function can be decomposed and allocated to twoindependent modules or subsystems.

Communication of the O2 values can be decomposed and allocated to twoindependent means, such as CAN bus (or similar serial communicationsbus) and discrete digital or analog I/O lines. At least one method maybe capable of placing O2 values onto the CAN bus (or similar serialcommunications bus).

If the O2 monitoring function is implemented with functionally-identicalsensors, a minimum of three sensors per zone may be used. A minimum oftwo sensors may be used if they avoid common-cause failures.

Faults of the O2 monitoring function may be diagnosed within ⅓ theperiod of the fault tolerant time interval in order to allow the systemto respond with the fault tolerant time interval. For systems with asensor count of N, if less than (N/2)+0.5 sensors per zone aredetermined to be operating properly, the O2 monitoring system maydefault to a safe state (O2 levels assumed to be unsafe).

Faults of the O2 monitor function may be transmitted via thecommunication means used for the module that has detected the fault.

If an O2 monitoring fault is detected, the system may display thisinformation via the ECP HMI and the DLP. The outcome of the fault(operation at a reduced level of reliability, or inhibited operation)may be communicated if possible.

If barometric compensation is determined to be necessary for proper O2sensing, this function may be implemented via a system with the samelevel of safety integration level as the O2 monitoring system.

The barometric compensation function may be decomposed and allocated totwo independent means (one each per means of O2 monitoring).

If O2 warm-up is required, then the monitoring function may assume thatthe O2 value is unsafe during the warm-up interval.

The operator protection mechanism may consist of a guarding system and awarning system. The function may be decomposed between these twomechanisms in a manner that accommodates users with vision or hearingdeficiencies, as well as distractions or impediments that may bereasonably expected during typical use.

A guard system may be provided to prevent the operator from entering thecargo hold when the O2 level is not safe. When the cargo hold isdetermined to be safe for entry, the guard may unlock upon user request.

The guard mechanism may provide a discrete output signal of its statusto the warn mechanism for the purpose of providing a rational check.

The guard mechanism may receive a discrete input signal from the warnmechanism for the purpose of providing a rational check. If the warnsystem output does not correlate with the guard system status, the guardmay not be released.

A means by which to warn the operator is be provided.

This mechanism may have an audible alert that is sufficiently loud to beheard in the average usage environment (such as a warehouse loadingdock). This function may be implemented with a system having no assessedlevel of functional safety, as this is not considered the primary meansof provision an operator warning. A door switch may be used todeactivate this system when the cargo hold door is closed.

A visual warning system using both color and position to provide a clearindication of “safe” (green lamp) or “not safe” (red lamp) may beimplemented. Labeling of the lamps may be provided to assist operatorswith vision color deficiencies. This system may be in operation wheneverthe system is capable of creating an environment that is potentiallydepleted of O2, and may not be defeated when the cargo hold door isclosed.

The warn mechanism may provide a discrete output signal of its status tothe guard mechanism for the purpose of providing a rational check.

The warn mechanism may receive a discrete input signal from the guardmechanism for the purpose of providing a rational check. If the warnsystem output does not correlate with the guard system status, thewarning system may indicate a potentially unsafe environment, and amessage may be transmitted via the CAN bus (or similar serialcommunications bus) indicating that this error exists.

Internal faults of the warning system may result in the warning systemindicating that O2 level is potentially unsafe. A message may betransmitted via the CAN bus (or similar serial communications bus)indicating that this error exists.

If warning faults occur, the system may display this information via theECP HMI and the DLP. The outcome of the fault (operation at a reducedlevel of reliability, or inhibited operation) may be communicated ifpossible.

The guard and warn functions may each use independent means of receivingO2 information.

A CAN bus (or similar serial communications bus) may be provided for thepurpose of communicating O2 values from the O2 sensing system to thewarning system.

Labeling and placards may be provided near the cargo hold entry and onthe gate locking mechanism (cable) to warn operators of this hazard.

A means to prevent the system from dispensing LN2 into an occupied cargohold may be provided.

The door switch function may be periodically monitored, and LN2dispensing may be inhibited whenever the door is not conclusivelydetermined to be closed.

Any door switch faults may be detected, and the system returned to asafe state within the fault tolerant time interval.

The guard system function may be periodically monitored, and LN2dispensing may be inhibited whenever the guard device is notconclusively determined to be locked in place.

Any guard device faults may be detected, and the system returned to asafe state within the fault tolerant time interval.

The valve control function may be monitored by the system. Any faultsmay be detected, and the system returned to a safe state within thefault tolerant time interval.

A device to prevent the system from operation (such as a lockable mainpower switch or lockable manual valve) may be provided to prevent thesystem from unintentional operation during storage or maintenance.

When the system is in standby mode, the temperature sensors may beperiodically monitored. A significant drop in temperature may result inthe system coming out of standby mode.

A manually-actuated mechanism by which to inhibit the release of LN2 bydeactivating the valve mechanism, or E-stop, may be provided.

The E-stop mechanism may include a set of normally-closed (N/C) contactsthat will open upon activation and interrupt power to the valves. TheE-stop mechanism may include a set of contacts that may be periodicallymonitored by the warning system (ASIL A).

Upon receiving a CAN message (or message via a similar serialcommunication bus) indicating E-stop actuation, valve operation may beimmediately ceased. The system shall sound its external alarm anddisplay a message.

This E-stop mechanism may be backlit for ease of location by anuntrained operator. A luminous (“glow-in-the-dark”) label may beprovided near the E-stop mechanism for ease of location by an untrainedoperator. This E-stop mechanism may be implemented by a latchingpushbutton, sized to be easily manipulated by an untrained operator. Thebutton may be recessed into the trailer sidewall to prevent damage oraccident operation. This E-stop mechanism may be diagnosed for faults bythe warning system. Any loss of correlation between multiple sets ofcontacts may result in a message being sent via the CAN bus (or similarserial communications bus). This error may result in the systemreturning to the safe state, and the system may display thisinformation.

The cargo door latch may be implemented in such a manner as to allow thedoor to be unlocked and opened from the interior of the trailer.

A label or placard may be provided near the cargo hold opening to warnoperators of this hazard and to instruct the operator to check the cargohold for the presence of other occupants prior to closing the cargo holddoor.

A vessel compliant with applicable geographical and industry standardsmay be utilized to reduce the risk of rupture during a normal use andmaintenance to a reasonable level.

A manual shutoff valve may be provided to allow a trained maintenancetechnician to isolate the vessel from other system elements. This valvemay have a means by which to lock out the valve.

A label or placard may be provided near the vessel to warn operators ofhazards related to ventilation function and the potential for injury dueto burst or rupture.

The system may monitor the valve pressure level. This measurement may becommunicated via the system CAN bus (or similar serial communicationsbus).

The system may warn the operator of an unsafe vessel pressure level.

The HMI may be utilized to provide a visual warning if the maximumvessel pressure level is exceeded.

The external alarm may be sounded if the maximum vessel pressure levelis exceeded.

A manual shutoff valve may be provided to allow an emergency responderto isolate the vessel from other system elements.

A “burst disk” may be present. There may be no means (automatic ormanual) by which to isolate the burst disk from the vessel.

The trailer body may provide a means by which to ventilate the cargohold to the outside environment at a rate sufficient to prevent theunacceptable rise of pressure.

For trailer equipped with outware-swinging doors, a label or placard maybe placed on the exterior of the door near the latch to warn of thispotential hazard.

Odorant: The ability of an operator to perceive the unintended releaseof LN2 may be improved via the additional of an odorant, such as sulfurdioxide (SO2).

Exemplary embodiments of a system and methods for cooling interiorvolumes of cargo trailers are described above in detail. The system andmethods are not limited to the specific embodiments described herein,but rather, components of the system and/or steps of the method may beutilized independently and separately from other components and/or stepsdescribed herein. For example, the system may also be used incombination with other temperature control systems and methods, and isnot limited to practice with only the cooling system as describedherein. Rather, an exemplary embodiment can be implemented and utilizedin connection with many other temperature control applications.

A controller, computing device, or computer, such as described herein,includes at least one or more processors or processing units and asystem memory. The controller typically also includes at least some formof computer readable media. By way of example and not limitation,computer readable media may include computer storage media andcommunication media. Computer storage media may include volatile andnonvolatile, removable and non-removable media implemented in any methodor technology that enables storage of information, such as computerreadable instructions, data structures, program modules, or other data.Communication media typically embody computer readable instructions,data structures, program modules, or other data in a modulated datasignal such as a carrier wave or other transport mechanism and includeany information delivery media. Those skilled in the art should befamiliar with the modulated data signal, which has one or more of itscharacteristics set or changed in such a manner as to encode informationin the signal. Combinations of any of the above are also included withinthe scope of computer readable media.

The order of execution or performance of the operations in theembodiments of the invention illustrated and described herein is notessential, unless otherwise specified. That is, the operations describedherein may be performed in any order, unless otherwise specified, andembodiments of the invention may include additional or fewer operationsthan those disclosed herein. For example, it is contemplated thatexecuting or performing a particular operation before, contemporaneouslywith, or after another operation is within the scope of aspects of theinvention.

In some embodiments, a processor, as described herein, includes anyprogrammable system including systems and microcontrollers, reducedinstruction set circuits (RISC), application specific integratedcircuits (ASIC), programmable logic circuits (PLC), and any othercircuit or processor capable of executing the functions describedherein. The above examples are exemplary only, and thus are not intendedto limit in any way the definition and/or meaning of the term processor.

In some embodiments, a database, as described herein, includes anycollection of data including hierarchical databases, relationaldatabases, flat file databases, object-relational databases, objectoriented databases, and any other structured collection of records ordata that is stored in a computer system. The above examples areexemplary only, and thus are not intended to limit in any way thedefinition and/or meaning of the term database. Examples of databasesinclude, but are not limited to only including, Oracle® Database, MySQL,IBM® DB2, Microsoft® SQL Server, Sybase®, and PostgreSQL. However, anydatabase may be used that enables the systems and methods describedherein. (Oracle is a registered trademark of Oracle Corporation, RedwoodShores, Calif.; IBM is a registered trademark of International BusinessMachines Corporation, Armonk, N.Y.; Microsoft is a registered trademarkof Microsoft Corporation, Redmond, Wash.; and Sybase is a registeredtrademark of Sybase, Dublin, Calif.)

This written description uses examples to disclose the invention,including the best mode, and also to enable any person skilled in theart to practice the invention, including making and using any devices orsystems and performing any incorporated methods. The patentable scope ofthe invention is defined by the claims, and may include other examplesthat occur to those skilled in the art. Other aspects and features ofthe present invention can be obtained from a study of the drawings, thedisclosure, and the appended claims. The invention may be practicedotherwise than as specifically described within the scope of theappended claims. It should also be noted, that the steps and/orfunctions listed within the appended claims, notwithstanding the orderof which steps and/or functions are listed therein, are not limited toany specific order of operation.

Although specific features of various embodiments of the invention maybe shown in some drawings and not in others, this is for convenienceonly. In accordance with the principles of the invention, any feature ofa drawing may be referenced and/or claimed in combination with anyfeature of any other drawing.

What is claimed is:
 1. A system for controlling a temperature within aninterior volume of a cargo trailer, comprising: a fluid distributionassembly including: a spray nozzle assembly configured to channel a flowof cryogenic cooling fluid into the interior volume of the cargotrailer; and a control valve coupled to the spray nozzle assembly forselectively channeling the flow of cryogenic cooling fluid through thespray nozzle assembly; and a monitoring system operatively coupled tothe fluid distribution assembly for controlling the flow of cryogeniccooling fluid into the interior volume, the monitoring systemcomprising: a temperature sensor configured to sense an ambienttemperature within the interior volume; and a processor programmed to:initiate a cooling operation including channeling the flow of cryogeniccooling fluid into the interior volume upon detecting a sensed ambienttemperature within the interior volume received from the temperaturesensor to be less than a predefined temperature; determine a flow rateof cryogenic cooling fluid based on a predefined rate of cooling and thesensed ambient temperature within the interior volume, and operate thefluid distribution assembly to channel the flow of cryogenic coolingfluid into the interior volume at the determined flow rate; monitor theambient temperature within the interior volume during operation of thefluid distribution assembly and determine an actual rate of cooling as afunction of changes in the ambient temperature within the interiorvolume over a predefined period of time; and operate the control valveto adjust the flow rate of cryogenic cooling fluid to reduce adifference between the actual rate of cooling and the predefined rate ofcooling; wherein the cargo trailer includes a cargo access door movablebetween an open position and a closed position, the monitoring systemincludes a position sensor configured to sense a position of the cargoaccess door, the processor is programmed to receive a signal from theposition sensor indicating the cargo access door is in the closedposition and initiate the cooling operation with the cargo access doorin the closed position; wherein the processor is programmed todiscontinue the cooling operation upon detecting the cargo access doorbeing moved to the open position; and wherein the monitoring systemincludes a plurality of oxygen sensors configured to sense an oxygenlevel within the interior volume and transmit signals indicating thesensed oxygen level to the processor, the processor is programmed to:determine a current level of oxygen within the interior volume upondetecting the cargo access door being moved to the open position andprovide a notification signal associated with the sensed oxygen level toan operator via a display device upon determining the current level ofoxygen is below a predefined level of oxygen.
 2. The system of claim 1,wherein the cargo trailer includes a cargo access door movable betweenan open position and a closed position, the monitoring system includes aposition sensor configured to sense a position of the cargo access door,the processor is programmed to receive a signal from the position sensorindicating the cargo access door is in the closed position and initiatethe cooling operation with the cargo access door in the closed position.3. The system of claim 2, wherein the processor is programmed todiscontinue the cooling operation upon detecting the cargo access doorbeing moved to the open position.
 4. The system of claim 1, wherein theprocessor is programmed to determine the current level of oxygen basedon sensed oxygen level received from a majority of the oxygen sensors.5. The system of claim 1, further comprising a cargo access assemblyincluding an electromechanical safety lock solenoid coupled to asidewall of the cargo trailer and a cable assembly removably coupled tothe electromechanical safety lock solenoid and extending to an oppositesidewall of the cargo trailer.
 6. The system of claim 5, wherein theprocessor is coupled to the electromechanical safety lock solenoid andconfigured to operate the electromechanical safety lock solenoid torelease the cable assembly upon determining the current level of oxygenis equal to or above the predefined level of oxygen.
 7. The system ofclaim 1, wherein the monitoring system includes a pressure sensorconfigured to measure an air pressure within the interior volume, theprocessor is programmed to receive signals from the pressure sensorindicating a sensed air pressure within the interior volume and toprovide a notification signal associated with the sensed air pressure toan operator via a display device upon determining the sensed airpressure is above a predefined air pressure value.
 8. The cargo trailercomprising: a plurality of sidewalls defining an interior volume; acargo access door movable between an open position and a closedposition; a fluid distribution assembly including: a spray nozzleassembly configured to channel a flow of cryogenic cooling fluid intothe interior volume; and a control valve coupled to the spray nozzleassembly for selectively channeling the flow of cryogenic cooling fluidthrough the spray nozzle assembly; and a monitoring system operativelycoupled to the fluid distribution assembly for controlling the flow ofcryogenic cooling fluid into the interior volume, the monitoring systemcomprising: a temperature sensor configured to sense an ambienttemperature within the interior volume; a position sensor configured tosense a position of the cargo access door; and a processor programmedto: initiate a cooling operation including channeling the flow ofcryogenic cooling fluid into the interior volume upon detecting a sensedambient temperature within the interior volume received from thetemperature sensor to be less than a predefined temperature; determine aflow rate of cryogenic cooling fluid based on a predefined rate ofcooling and the sensed ambient temperature within the interior volume,and operate the fluid distribution assembly to channel the flow ofcryogenic cooling fluid into the interior volume at the determined flowrate; monitor the ambient temperature within the interior volume duringoperation of the fluid distribution assembly and determine an actualrate of cooling as a function of changes in the ambient temperaturewithin the interior volume over a predefined period of time; and operatethe control valve to adjust the flow rate of cryogenic cooling fluid toreduce a difference between the actual rate of cooling and thepredefined rate of cooling; wherein the processor is programmed toreceive a signal from the position sensor indicating the cargo accessdoor is in the closed position and initiate the cooling operation withthe cargo access door in the closed position; wherein the processor isprogrammed to discontinue the cooling operation upon detecting the cargoaccess door being moved to the open position; and wherein the monitoringsystem includes a plurality of oxygen sensors configured to sense anoxygen level within the interior volume and transmit signals indicatingthe sensed oxygen level to the processor, the processor is programmedto: determine a current level of oxygen within the interior volume upondetecting the cargo access door being moved to the open position andprovide a notification signal associated with the sensed oxygen level toan operator via a display device upon determining the current level ofoxygen is below a predefined level of oxygen.
 9. The cargo trailer ofclaim 8, further comprising a cargo access door movable between an openposition and a closed position, the monitoring system includes aposition sensor configured to sense a position of the cargo access door,the processor is programmed to receive a signal from the position sensorindicating the cargo access door is in the closed position and initiatethe cooling operation with the cargo access door in the closed position.10. The cargo trailer of claim 9, wherein the processor is programmed todiscontinue the cooling operation upon detecting the cargo access doorbeing moved to the open position.
 11. The cargo trailer of claim 8,wherein the processor is programmed to determine the current level ofoxygen based on sensed oxygen level received from a majority of theoxygen sensors.
 12. The cargo trailer of claim 8, further comprising acargo access assembly including an electromechanical safety locksolenoid coupled to a sidewall of the cargo trailer and a cable assemblyremovably coupled to the electromechanical safety lock solenoid andextending to an opposite sidewall of the cargo trailer.
 13. The cargotrailer of claim 12, wherein the processor is coupled to theelectromechanical safety lock solenoid and configured to operate theelectromechanical safety lock solenoid to release the cable assemblyupon determining the current level of oxygen is equal to or above thepredefined level of oxygen.
 14. The cargo trailer of claim 8, whereinthe monitoring system includes a pressure sensor configured to measurean air pressure within the interior volume, the processor is programmedto receive signals from the pressure sensor indicating a sensed airpressure within the interior volume and to provide a notification signalassociated with the sensed air pressure to an operator via a displaydevice upon determining the sensed air pressure is above a predefinedair pressure value.
 15. A method for operating a system including amicroprocessor programmed to control a temperature a within an interiorvolume of a cargo trailer, comprising the microprocessor implementingthe steps of: receiving a signal from a temperature sensor indicating asensed ambient temperature within the interior volume; and initiating acooling operation upon detecting the sensed ambient temperature withinthe interior volume to be less than a predefined temperature, including:determining a flow rate of cryogenic cooling fluid based on a predefinedrate of cooling and the sensed ambient temperature within the interiorvolume; operating a control valve to channel a flow of cryogenic coolingfluid through a spray nozzle assembly into the interior volume at thedetermined flow rate; monitoring the ambient temperature within theinterior volume during operation of the control valve and determine anactual rate of cooling as a function of changes in the ambienttemperature within the interior volume over a predefined period of time;and operate the control valve to adjust the flow rate of cryogeniccooling fluid to reduce a difference between the actual rate of coolingand the predefined rate of cooling; receiving a signal from a positionsensor indicating a position of a cargo access door of the cargotrailer; and initiating the cooling operation upon detecting the cargoaccess door in a closed position, and discontinuing the coolingoperation upon detecting the cargo access door being moved to an openposition; receiving signals from a plurality of oxygen sensorsindicating a sensed oxygen level within the interior volume; determininga current level of oxygen within the interior volume based on thesignals received from the oxygen sensors upon detecting the cargo accessdoor being moved to the open position; and providing a notificationsignal associated with the sensed oxygen level to an operator via adisplay device upon determining the current level of oxygen is below apredefined level of oxygen.
 16. The method of claim 15, including themicroprocessor performing the steps of: receiving a signal from aposition sensor indicating a position of a cargo access door of thecargo trailer; and initiating the cooling operation upon detecting thecargo access door in a closed position, and discontinuing the coolingoperation upon detecting the cargo access door being moved to an openposition.
 17. The method of claim 15, including the microprocessorprogrammed to: receive signals from a pressure sensor indicating asensed air pressure within the interior volume; and provide anotification signal associated with the sensed air pressure via thedisplay device upon determining the sensed air pressure is above apredefined air pressure value.